It is often desirable to provide an analog video signal to multiple devices from a single video source. For example, multiple external monitors may be connected to a video source. Additionally, video signals are sometimes provided from a video source to a video capture device (VCD) that captures the video signal and transmits the signal to a remote monitoring site while simultaneously being provided to a local monitor. There are methods of providing a single video signal to multiple devices while minimizing signal degradation. One such method is to use an active video splitter. A video splitter splits a single video signal input into multiple output signals. The video input is terminated, then each output signal has a buffer to drive the signal into each load.
According to standards set forth by the Video Electronics Standards Association (VESA), a typical Video Graphics Array (VGA) video source has for each of a red, blue, and green signal, a 2X buffer followed by 75-Ohm resistor connected in series. Because the bandwidth of VGA is very high, the video signal must be terminated correctly in order to maintain a clean signal. Therefore, within a video receiving device such as a monitor, each signal must have a 75-Ohm parallel termination resistor followed by a receiving buffer. Using the video splitter described above, each video signal created by a split is driven using the required buffer and resistor. Each signal is properly terminated at the destination device according to VGA standards. If a device is disconnected from one of the split signals, the other signals will not be affected since each signal is independently amplified and terminated. However, there are several disadvantages to this method of splitting a video signal.
First, each output signal requires a VGA connector. For example, if a splitter splits a single video signal into three output video signals, three VGA connectors are required on the output side of the splitter, one for each cable connecting the signal to a corresponding video device. This requires the splitter to be at least as big as the corresponding VGA connectors. These splitters are often external boxes that increase the external space requirements. Additionally, multiple cables are also required, creating a need for additional space as well as adding to the visually unappealing bundle of cables behind a computer. Finally, because splitters compensate for signal loss using buffers, the buffers also amplify the noise in a signal, creating a certain amount of signal degradation.
Another method of providing a video signal to multiple devices may be illustrated using an example environment comprising a single video source, a video capture device, and a local monitor. Because the video source and monitor contain the necessary electrical components to properly terminate the video signal, the video signal within the cable may be additionally routed to the video capture device as long as the VCD does not terminate the video signal. If the VCD were to terminate the signal, then the voltage at the monitor would be reduced, causing the display quality to be significantly reduced. Therefore, as long as the monitor receives the video signal and as long as the VCD does not terminate the signal, the video signal quality remains intact. A problem arises, however, when the local monitor is disconnected from this system since the video signal would no longer be properly terminated. Existing VCDs, monitors, and video cables do not provide the flexibility of being able to be used in a system that includes a local monitor, a system that does not include a local monitor, and a system to which a local monitor is periodically attached without modification.
It is with respect to these and other considerations that the various embodiments of the present invention have been made.